docs/zh_CN: add dt kernel-api translation

Translte .../devicetree/kernel-api.rst into Chinese.

Signed-off-by: Yanteng Si <siyanteng@loongson.cn>
Reviewed-by: Alex Shi <alexs@kernel.org>
Link: https://lore.kernel.org/r/35fd1b5801d7191e078937908008115f8949aac3.1662449105.git.siyanteng@loongson.cn


Signed-off-by: Jonathan Corbet <corbet@lwn.net>